Generally, a fuel cell is similar to other electrochemical cells in that there is an electrolyte (e.g., liquid or solid) and two electrodes (e.g., a cathode and an anode) at which the electrochemical reaction occurs. However, the fuel cell is distinguished from a conventional battery by its fuel storage capacity and in that its electrodes are catalytically active. A fuel cell is used to convert the stored energy of a fuel (e.g., hydrogen gas or methanol) into electrical energy.
The electrochemical reactions of the fuel cell required for the conversion includes oxidation of the fuel (e.g., hydrogen or methanol) at the anode and reduction of oxygen at the cathode. As the fuel is oxidized at the anode electrons are given up to an external electrical load and the oxidant (oxygen) accepts electrons and is reduced at the cathode. Ionic current through an electrolyte completes the circuit.
As a result of the nature of these reactions it is necessary for the electrodes to be designed to allow gaseous reactants and/or products to diffuse into and/or out of the electrode structures. The electrodes are specifically designed to be porous to allow gas diffusion and maximize the contact between the reactants and the electrode to optimize the reaction rate. One type of electrode commonly used is a membrane electrode assembly (hereafter referred to as “MEA”) which is typically made of an ionically conducting polymeric membrane sandwiched between two electronically conducting electrodes.
The electrolyte is required to be in contact with both electrodes and is either acidic or alkaline and takes the form of a solid or a liquid depending on the particular application. For example, in a proton-exchange membrane fuel cell, the electrolyte is a solid proton-conducting polymer membrane, (e.g., perfluorosulphonic acid materials). Generally, the electrolyte must remain hydrated during operation in order to prevent loss of ionic conduction through the electrolyte. As a result of the necessity for hydration, the limits of the operating temperature of the PEMFC are between 70° C. and 120° C.
The relatively low operating temperatures of fuel cells require the use of electrocatalysts in order for the oxygen reduction and hydrogen oxidation reactions to proceed at useful rates. Noble metals, in particular platinum, have been found to be the most efficient and stable electrocatalysts for hydrogen oxidation in low-temperature fuel cells. Generally, the noble metal electrocatalyst is provided as small particles of high surface area, which are often, but not always, distributed on and supported by larger macroscopic conducting carbon particles to provide a desired catalyst loading. Conducting carbons are the preferred materials to support the catalyst. However, while supported platinum catalysts have demonstrated high activity for hydrogen oxidation, this proclivity for facile kinetics is severely retarded with carbon monoxide concentrations of only a few ppm.
Many fuel cell systems use reformed fuels, which are formed through a process whereby a hydrogen fuel is produced by converting a hydrocarbon-based fuel such as methane, or an oxygenated hydrocarbon fuel such as methanol, to hydrogen. In addition to hydrogen, the reformate fuel contains high levels of carbon dioxide (e.g., about 25%) and impurities, such as carbon monoxide (about 1%). In contrast, direct or non-reformed fuel cells oxidize fuel high (e.g., lower primary alcohols including methanol and ethanol) in hydrogen content directly, without the hydrogen first being separated by a reforming process are particularly useful. For example, in a typical methanol fuel cell, methanol is oxidized to produce electricity, heat, water, and carbon dioxide shown in the equation:Anode: CH3OH+H2O→CO2+6H++6e−Cathode: O2+4e−+4H+→2H2ONet: 2CH3OH+3O2→4H2O+CO2 
Platinum (Pt) is the best catalyst for many electrochemical reactions, including methanol oxidation. One major obstacle to the development of platinum containing catalytic electrodes for electrochemical reactions is the expense associated with the use of platinum metal. Another major obstacle in the development of platinum containing catalytic electrodes for electrochemical reactions is the loss of electrochemical activity due to “poisoning” by carbon monoxide (e.g., an intermediate in the oxidation of methanol to carbon dioxide). The CO molecule is strongly adsorbed on the electroactive surface of the electrode, obstructing the oxidation of new fuel molecules.
Various unsuccessful attempts have been made to find a solution to the CO poisoning problem; however, results have proven to be too expensive, ineffective or impractical to be commercially viable. Thus, there remains a need for electrocatalysts that are resistant to CO poisoning and can be used on the anode for alcohol oxidation in fuel cells.
Furthermore, current approaches in the art have yielded some materials that have improved electrocatalytic activities and are less expensive than pure Pt catalysts; however, the costs associated with these materials are still prohibitive for full exploitation of fuel cell technology. Other approaches are to completely remove Pt from these systems and replace it with less expensive materials, while retaining catalytic activity at least equal to that of Pt. For example, electroreduction of oxygen at non-platinum metallic combinations,4 inorganic and organometallic complexes,5 transition metal oxides,6 calchogenides,7 and enzyme electrodes8 have been studied. Despite the extensive research that has been carried out in this area, the detailed mechanism of the ORR, even at Pt, is still uncertain.9 
The foregoing problems have been recognized for many years and while numerous solutions have been proposed, none of them adequately address all of the problems in a single device, e.g., electrodes that retain acceptable electrocatalytic activity while being resistant to CO poisoning and providing a less expensive material than pure Pt catalysts.